Process Technology
A typical re-refining process is consist of the following steps.

Pre-treatment:
Filtration and de-watering of the waste oil by decantation.

De-watering:
De-watering and light hydrocarbon removal by distillation.

Diesel removal:
Removal of diesel fraction (C7-C12) by distillation.

Asphaltene removal:
Removal of asphaltic fraction by thin film evaporator. High temperature and high vacuum is needed.

Finishing:
After removing water, light hydrocarbons and asphaltic fraction, chemical treatment of the waste oil by solvent extraction or hydrogenation.

Fractionation:
Having different cuts of base oil according to their boiling points.